|Year : 2020 | Volume
| Issue : 1 | Page : 30-35
Respiratory and hemodynamic effects of positive end-expiratory pressure during capnoperitoneum for laparoscopic cholecystectomy
Ravishankar Murugesan, Sivashanmugam Thiagarajan, Parthasarathy Srinivasan
Department of Anesthesiology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth University, Puducherry, India
|Date of Submission||22-Sep-2019|
|Date of Decision||28-Oct-2019|
|Date of Acceptance||22-Nov-2019|
|Date of Web Publication||13-Oct-2020|
Prof. Parthasarathy Srinivasan
Department of Anesthesiology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth University, Puducherry
Source of Support: None, Conflict of Interest: None
Background: General anesthesia, muscle paralysis, and increased intra-abdominal pressure are known to produce basal lung atelectasis and may contribute to the inadequate CO2removal and increased end-tidal carbon dioxide (EtCO2)during laparoscopic surgery. Positive end-expiratory pressure (PEEP) has been shown to prevent compression atelectasis during general anesthesia. Hence, we designed this study to test the hypothesis that the application of PEEP before capnoperitoneum will maintain EtCO2 within the normal range without changing the ventilator parameters. Our secondary outcome measures were hemodynamic changes during PEEP and capnoperitoneum. Methods: Sixty patients were randomly allocated to receive 0 PEEP (n = 30) or 10 PEEP (n = 30) with constant minute ventilation under standardized general anesthesia. Respiratory and hemodynamic parameters were recorded every 2 min for 10 min then every 5 min till 30 min after capnoperitoneum. Results: In group PEEP-0, the mean EtCO2increased significantly after 2 min of capnoperitoneum, plateaued at 15 min, remained at high level till 30 min (34.1 ± 3.1 to 43.3 ± 2.9 mmHg; P = 0.000). In group PEEP-10, EtCO2dropped from the baseline (36.5 ± 3.2 to 32.0 ± 3.3 mmHg; P = 0.0003) at 5 min after the application of PEEP, and there was no net increase in EtCO2following capnoperitoneum till 30 min (34.5 ± 3.5 mmHg). Cardiac output fell significantly after the induction in both groups but did not fall any further after the application of PEEP and capnoperitoneum. Conclusion: The application of PEEP of 10 cm H2O before the creation of capnoperitoneum can maintain EtCO2within the normal range without making changes in the ventilator parameters, with stable hemodynamics in patients undergoing laparoscopic cholecystectomy.
Keywords: Cardiac output, laparoscopy, pneumoperitoneum, positive end-expiratory pressure
|How to cite this article:|
Murugesan R, Thiagarajan S, Srinivasan P. Respiratory and hemodynamic effects of positive end-expiratory pressure during capnoperitoneum for laparoscopic cholecystectomy. J Datta Meghe Inst Med Sci Univ 2020;15:30-5
|How to cite this URL:|
Murugesan R, Thiagarajan S, Srinivasan P. Respiratory and hemodynamic effects of positive end-expiratory pressure during capnoperitoneum for laparoscopic cholecystectomy. J Datta Meghe Inst Med Sci Univ [serial online] 2020 [cited 2020 Oct 28];15:30-5. Available from: http://www.journaldmims.com/text.asp?2020/15/1/30/297964
| Introduction|| |
It has been established that there is a reduction in functional residual capacity (FRC) following general anesthesia and muscle paralysis because of the reduction in thoracic volume. This reduction in thoracic volume primarily contributes to the development of basal atelectasis, increased dead-space ventilation, and intrapulmonary shunts. This is further aggravated by the increased intra-abdominal pressure (IAP) during laparoscopic surgery and contributes to the increased end-tidal carbon dioxide (EtCO2) during capnoperitoneum., Conventionally, minute ventilation is increased to maintain EtCO2 within the normal range during general anesthesia., It was postulated that under spinal anesthesia preserved diaphragmatic tone prevents basal atelectasis and maintains the FRC. The application of positive end-expiratory pressure (PEEP) was demonstrated to prevent compression atelectasis and maintain FRC during general anesthesia. Hence, we designed this study to test the hypothesis that the application of PEEP before capnoperitoneum can maintain EtCO2 within the normal range without changing the ventilator parameters. Our secondary outcome measures were hemodynamic changes during PEEP and capnoperitoneum.
| Methods|| |
This randomized controlled study was conducted at a tertiary care institution between January 2016 and December 2017. The Institutional Research and Ethics Committee reviewed the study protocol and approved the same (faculty-2014/33-MGMCRI).
Sixty ASA I and II patients between the age group of 15–60 years scheduled to undergo elective laparoscopic cholecystectomy were selected by a computer-generated random sample during the study period of 2 years. Informed consent was obtained from all the patients. Patients with preexisting pulmonary disease, cardiovascular disease, neuromuscular disease, and pregnant patients were excluded from the study.
All the patients were premedicated with oral diazepam 10 mg night before and in the morning of surgery. Oral metoclopramide 10 mg and intramuscular morphine 0.15 mg/Kg were given 60 min before the surgery. In the operating room, baseline electrocardiogram, heart rate (HR), mean arterial pressure (MAP), and hemoglobin oxygen saturation were recorded using a GE S5 monitor. The noninvasive cardiac output (NICO monitor–L and T) was used to measure the cardiac output. The monitor uses the principle of impedance plethysmography using eight electrodes that measures cardiac output between 0.5 L/min and 20 L/min with an accuracy of ± 15%. Baseline arterial blood gases (ABGs) after establishing an arterial line was obtained, and 500 ml of lactated Ringer's solution was infused over 10 min. Anesthesia was induced with 5 mg/Kg of thiopentone, and tracheal intubation was accomplished with 0.15 mg/Kg of vecuronium bromide. Baseline EtCO2 was measured after intubation. Anesthesia was maintained with age adjusted 1.0 MAC of isoflurane in a mixture of 67% nitrous oxide in 33% oxygen using GE Aisys CS2 station. Incremental dose of morphine was used to provide intraoperative analgesia, and neuromuscular blockade was maintained with increments of vecuronium bromide. After induction, the ventilator was set to deliver a tidal volume of 10 ml/Kg, respiratory rate 12/min with an I: E ratio of 1:2, and the fresh gas flow was 100 ml/Kg/min. After 10 min, flow rate was decreased to 1 L/min with 50% nitrous oxide and oxygen, and postinduction steady state parameters were recorded. At this point, each patient was randomized to one of the two groups (Group PEEP-0 or Group PEEP-10) by the sealed-envelope technique and appropriate PEEP of either 0 or 10 cm H2O was applied. The ventilation parameters were kept constant from the beginning to the end of the case. ABG was performed 5 min after the allocation of groups.
The automatic insufflator was set to maintain the IAP at 14 mmHg, and the capnoperitoneum was created with CO2 by the surgeon. The data such as HR, MAP, NICO, EtCO2, Ppeak, and Pmean were recorded every 2 min for the first 10 min and every 5 min till 30 min. ABG was repeated at the end of 30 min of capnoperitoneum. The alveolar dead space to tidal-volume ratio (VD/VT) was calculated using the equation VD/VT= 1.135 × (PaCO2- EtCO2)/PaCO2–0.005.
At the end of the surgery, anesthesia was terminated, and residual neuromuscular blockade was antagonized with a mixture 50 μg/Kg neostigmine and 10 μg/Kg glycopyrrolate. Tracheal extubation was done when the patient was fully awake.
Data were collected and analyzed using the SPSS software program (version 16). Sample size was based on a pilot study done in ten patients (not included in the study), which revealed that 20% difference in the highest EtCO2 value observed during the study period between PEEP-10 (32 mmHg ± 3.3) and PEEP-0 (41 ± 3.8 mmHg) groups with power of 0.8 and alpha error of 0.05. The distribution of data was determined by the Kolmogorov–Smirnov test. Intergroup differences between the variables recorded were analyzed by the t test. P < 0.05 was considered statistically significant.
| Results|| |
The physical characteristics and baseline parameters were similar in both the groups [Table 1]. Normality was established with the Kolmogorov–Smirnov test. In group PEEP-0, the mean EtCO2 increased significantly after 2 min of capnoperitoneum and plateaued at about 15 min but remained at high level till 30 min (34.1 ± 3.1–43.3 ± 2.9 mmHg; P = 0.000), whereas in the group PEEP-10, we observed a significant drop in the EtCO2 from the baseline (36.5 ± 3.2–32.0 ± 3.3 mmHg; P = 0.0003) at 5 min after the application of PEEP, and there was no net increase in EtCO2 following capnoperitoneum till 30 min (34.5 ± 3.5 mmHg) when compared to the baseline value [Figure 1]. Correspondingly, the mean PaCO2 was high (46.0 ± 4.1 vs. 35.27 ± 3.9 mmHg) with higher PaCO2–EtCO2 gradient (2.77 ± 4.01 vs. 1.35 ± 2.96 mmHg; P = 0.019) in the group PEEP-0 at 30 min The dead-space ventilation (VD/VT) was significantly increased from the baseline when compared to 30 min in PEEP-0 group (6.87 ± 7.21 vs. 12.05 ± 8.1%; P = 0.0062), whereas there was no change in the PEEP-10 group (8.93 ± 9.22 vs. 9.29 ± 7.95; P = 0.354). The oxygenation was better preserved with significantly higher PaO2/Fio2 ratio in PEEP-10 group. The acid base status was well maintained in the PEEP10 group [Figure 2].
|Figure 1: ETCO2 in patients receiving (--•-- ) 0 PEEP or (- -⧫ - -) 10 PEEP. * P < 0.05, there is significant difference between the groups. Baseline: baseline value or preoperative value, postinduction (10 min): 10 min postinduction value, post-PEEP (5 min): 5 min postPEEP value, 2 min: 2 min postcapnoperitoneum value, 4 min: 4 min postcapnoperitoneum value, 6 min: 6 min postcapnoperitoneum value, 8 min: 8 min postcapnoperitoneum value, 10 min: 10 min postcapnoperitoneum value, 15 min: 15 min postcapnoperitoneum value, 20 min: 20 min postcapnoperitoneum value, 25 min: 25 min postcapnoperitoneum value, 30 min: 30 min postcapnoperitoneum value|
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|Figure 2: Gas exchange in patients receiving (–•– & )0PEEP or (- - ⧫ - - & ) 10PEEP. * P < 0.05, there is significant difference between the group PEEP-10 and group PEEP-0. # P < 0.05, there is significant difference within the group PEEP-0 (between baseline and 30 min postcapnoperitoneum values). Baseline: baseline value or preoperative value, post-PEEP (5 min): 5 min postPEEP value, 30 min: 30 min postcapnoperitoneum value|
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Following induction of anesthesia, the cardiac output fell by 690 ± 450 ml/min in group PEEP-0 and 680 ± 320 ml/min in group PEEP-10; P < 0.0001 when compared to the preinduction value. There was no further change in CO2 following the application of PEEP 0 (65 ± 30 ml/min; P = 0.29) or PEEP 10 (72 ± 34 ml/min; P = 0.25) and 14 mmHg capnoperitoneum (82 ± 38 ml/min; P = 0.29 and 80 ± 41 ml/min; P = 0.34) in both the groups, respectively [Figure 3]. In PEEP-10 group, peak and mean airway pressures demonstrated a significant increase after the application of PEEP till 30 min, (P < 0.05). The changes in HR and MAP were comparable in both the groups [Figure 3]. The calculated dead-space ventilation VD/VT(6.87 ± 7.21 vs. 12.05 ± 8.1%; P = 0.0062) and PaCO2–EtCO2 gradient (2.77 ± 4.01 vs. 1.35 ± 2.96 mmHg; P = 0.019) were significantly increased at 30 min when compared to the baseline in PEEP-0 group. This was not so in PEEP-10 [Chart 1].
|Figure 3: Heart rate. Mean arterial pressure and cardiac output in patients. Baseline: baseline value or preoperative value, Postinduction (10 min): 10 min postinduction value, Post-PEEP (5 min): 5 min post-PEEP value, 2 min: 2 min postcapnoperitoneum value, 4 min: 4 min postcapnoperitoneum value, 6 min: 6 min postcapnoperitoneum value, 8 min: 8 min postcapnoperitoneum value, 10 min: 10 min postcapnoperitoneum value, 15 min: 15 min postcapnoperitoneum value, 20 min: 20 min postcapnoperitoneum value, 25 min: 25 min postcapnoperitoneum value, 30 min: 30 min postcapnoperitoneum value|
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| Discussion|| |
We have demonstrated that by the application of 10 cmH2O PEEP, normocapnia could be maintained without changing the ventilator parameters and without hemodynamic disturbance in patients undergoing laparoscopic cholecystectomy.
In PEEP-0 group, the mean EtCO2 increased significantly than in group PEEP10. Lister et al. while studying the effect of IAP on exhaled CO2(VCO2) observed an increase from 139 ± 23 ml/min to 172 ± 30 ml/min (P ≤ 0.001) when IAP increased from 0 to 10 mmHg. VCO2 did not increase any further despite increasing IAP to 25 mmHg (166 ± 20 ml/min). They proposed that based on Fick's principle for a given IAP, the maximal peritoneal surface area is recruited over a period of time and after that the CO2 absorption, and hence, the CO2 load on the respiratory system for elimination was static.
In the PEEP-10 group, we observed a significant drop in the EtCO2 from the baseline (36.5 ± 3.2–32.0 ± 3.3 mmHg; P = 0.0003) at 5 min after the application of PEEP, and there was no net increase in EtCO2 till 30 min (34.5 ± 3.5 mmHg) when compared to the baseline value. The initial drop in the EtCO2 following the application of 10 cm H2O PEEP indicates an improved alveolar ventilation which was possibly adequate enough to eliminate the subsequent increased CO2 load from the capnoperitoneum. This hypothesis can be better explained by the effect of PEEP on the pressure volume curve of any lung. Normally, pulmonary Zone 2 and 3 (west) lies in the steep portion of the pressure volume curve, with Zone 4 lying close to the lower inflection point and Zone 1 close to the upper inflexion point. Induction of anesthesia, paralysis, and increased IAP increasingly move the Zone 2 and 3 toward less favorable lower inflection point and increases the volume of Zone 4 (atelectasis) and facilitates shunting. Because of the low compliant unfavorable position, the effective alveolar ventilation comes down for the given minute ventilation. The application 10 PEEP reduces the volume of Zone 4 and moves the Zone 2 and 3 back to the steeper portion of the PV cure and increases the alveolar ventilation with the same minute ventilation.
A recent study has shown an increase in EtCO2 even after the application of 10 cm H2O PEEP when it was applied after the creation of capnoperitoneum. It is imperative to apply PEEP before creating capnoperitoneum and prevent derecruitment of the alveoli. Recruitment after collapse may not be very effective and can expose the alveoli to “atlectrauma” as these alveoli will be subjected to repeated opening and collapse. A different study also demonstrated the beneficial effects of applying PEEP before capnoperitoneum on respiratory and cardiovascular function where the results are similar to our study.
This explanation further correlates with the observation that the calculated dead-space ventilation significantly increased at 30 min when compared to the baseline in PEEP-0 group. This was not so in PEEP-10 group. Anderson et al. clearly demonstrated with the high-resolution computed tomography that the induction of capnoperitoneum increases the mean atelectasis volume in the dependent lung region by 66% (range 11%–170%), and the diaphragm was cranially displaced by 1–3 cm (mean 1.9 cm) with 11–13 mmHg IAP during laparoscopic cholecystectomy. The application of PEEP helped us to prevent this atelectasis by increasing the FRC. In yet another study, the authors have shown during laparoscopic surgery that the application of 10 PEEP increased the end-expiratory lung volume by 570 ml in healthy patient and 367 ml in obese patient, and this amounts to 46% increase when compared with PEEP-0 (P = 0.001).
In our study, we observed that the cardiac output fell about 0.6l/min after the induction of anesthesia in both the study groups but did not fall any further after the application of PEEP and capnoperitoneum. This observation is in contrast to another study where they has demonstrated significant drop in cardiac output (3.6 ± 2.1–1.6 ± 1.0 l/min; P < 0.01) when 10 cm of PEEP combined with 15 cm IAP and concluded that both pressures should not be combined in clinical practice. In this study, the authors measured all the changes in the cardiac output within 15 min of induction without giving adequate time for hemodynamic stabilization between each maneuvers. Russo et al., in their recent study, clearly demonstrated that 10 cm of PEEP improved cardiac and pulmonary function by recruiting basal alveoli, therefore, improving oxygenation and enhancing CO2 washout and inhibition of the vasoconstrictor reflex, with a consequent reduction in pulmonary arterial systolic pressure and stroke work. The initial drop in EtCO2 in our study was not attributed to the hemodynamic consequences of PEEP because the fall in cardiac output was noted after the induction of anesthesia in both the groups, and there was no change after the application of PEEP. In yet another study, Bernard et al. 16 have shown that the application of PEEP on a preestablished pneumoperitoneum during laparoscopic liver resection in normovolemic patients did not decrease cardiac index. The changes in the PaCO2 follow EtCO2 trend in both groups but with a higher PaCO2–EtCO2 gradient in PEEP-0 group. Since we have not measured the PaCO2 at multiple intervals, we could not comment on the pattern of increase. A few authors have established the maintenance of respiratory and cardiac parameters after capnoperitoneum by using PEEP, but their emphasis was not on maintaining the set ventilator parameters., We did not change any respiratory settings except the application of PEEP to clearly establish the effect of PEEP on various parameters.
The limitations of our study are we measured the effect of PEEP only up to 30 min of capnoperitoneum. Furthermore, because of ethical reasons, only three arterial blood gas samples were taken, and all our patients were ASA I and II patients. Further studies are required to evaluate the effect of PEEP and IAP on patients with cardiorespiratory compromise. Hence, we recommend that the early application of PEEP should be considered to facilitate CO2 elimination during laparoscopic cholecystectomy.
| Conclusion|| |
The application of a PEEP of 10 cm H2O before the creation of capnoperitoneum can maintain EtCO2 within the normal range without making changes in ventilator parameters, with stable hemodynamics in patients undergoing laparoscopic cholecystectomy. Hence, we recommend the more physiological way of maintaining CO2 removal during laparoscopic surgery by the institution of PEEP before capnoperitoneum.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]